Stain and rust removing composition



May 1l, 1965 1..HAH y 3,183,191 STAIN AND RUSTREMOVING COMPOSITIONvlrilealmprn 119. Aseo 40 30 Z0 /0 0 50M/M HYDHOSULFITE 60 70 80 .90 /w50B/UM H/SULf/TE QS l /wsr Hmm/ff? coms/non wam.: ppm a/sozvf/J ma /5mus mams' 3 l Rfammfa i IN VEN TOR..

01214561890//12/3 l x NUMBER 0f sofrNf/f mmf/0N omis. y WM C H06 iWMA/'4 )620mm lposition of the above character.

United States Patent 3,l83,l91 STAIN AND RUST REMOVING COMPOSITONClifford C. Hach, Ames, Iowa, assignor to Hach Chemical Company, Ames,Iowa, a corporation of Iowa Filed Apr. 19, 1960, Ser. No. 23,190 5Claims. (Cl. 252-405) The present invention relates to a composition fordissolving and removing stains and particularly for dissolving rust andremoving rust stains. More specifically, the

invention relates to a composition finding particular, but notnecessarily exclusive, utility for removing rust from water softeningequipment, from ion exchange resins and minerals used in such equipment,and from other surfaces and objects on which rust and like stainsaccumulate.

The invention has as its principal objective the removal of rustaccumulations from equipment such as'water softening equipment and ionexchange resins in which the efficiency is reduced as .rust collects,and the removal of rust stains '.and-likegsurfacestains fromsinks,walls, andA the appearance of which is adversely affected by tequipment, ion exchange apparatus, and the ion exchange resins andminerals used therein.

Another object of the present invention is to provide a rust and stainremoving composition which can be incorporated into*l detergents,Cleansers, soaps and the like for household and industrial use.

Still another object of the present invention is to provide a rustremoving composition of the foregoing character which is inexpensive, issimple and economical to use,

which is highly effective in removing rust, rust stains and like stainsand precipitates, and which does not leave a residual or unsightly darkprecipitate in place of the stain removed. A further and more detailedobject of the in'- vention is to provide a composition of the above typewhich is capable of removing rust stains from sinks, floors, walls,automobile surfaces and the like.

A related object of the present inventionl is to provide an improvedmethod for making a rust removing corn- Still a further object is toprovide sucha process which is inexpensive, simple to operate and whicheiciently produces a rust removing composition of the desired characterwithout necessitating the batching and mixing of various dry powdercomponents.

Still a further object of the invention is to provide an improved watersoftener regenerating composition which contains therein an addition tothe regenerating salt a rust removal and rust preventative substanceembodying the present invention.

Other objects and advantages of the present invention will becomeapparent as'the following description proceeds taken in connectionwith`the accompanying drawings wherein:

FIGURE l is a schematic flow diagram illustrating a process forproducing the rust and stain removing composition embodying the presentinvention.

FIG. 2 is aV chart illustrating the amount of rust dissolved as afunction of the rust remover composition.

FIG. 3 is a chart illustrating the effect of using the rust removingcomposition embodying the invention in a water treatment regeneratingcomposition.

The present invention is embodied in a composition of salts which areactive in aqueous solution to dissolve or remove stains such as ironoxide or rust. While these salts taken individually might have someeffect in dissolving or removing .rust and like stains, it .is in theparticular combination of salts, wherein the salts act togethersynergistically to remove or dissolve a greater amount of rust and stainthan is possible using the salts individually, that the presentinvention resides. More specifically, the composition embodying thepresent invention involves a mixture of active salts, namelysodiumhydrosulte (Na2S2O4) and sodium bisulfite (NaHSOs), or sodiummetabisulfite (NazSZO) also known as sodium pyrosulte. While referencehas been made to the sodium salts, it should be understood that othermetal salts of a similar type can be employed, such as the potassiumsultesalts. When a mixture of these salts, such as the sodiumhydrosuliite and sodium bisultite, is stored in dry powder form, thesalts are reasonably stable although they should be maintained in asealed container. Upon addition to or inthe presence of water, however,the salts are dissolved thereby `becoming .capable of reacting withrust, iron oxide or other stains present whether on sinks, porcelaincontainers, water softeners, walls, automobiles or the like. This stainremoving composition when dissolved in water is believed toreact withrust, for example, according to the following equation representing theaqueous reaction:

Sodium Sodium Rus tv Iron Sodium hydroblsultlte (insolsultlto sultltesulto uhle) (soluble) It is believed that in the reaction the sodiumhydrosultite is effective to reduce the insoluble rust (ferrie ironoxide) to a lower iron oxide which then reacts with the bisulfite and ischanged to the more soluble form of ferrous sulfite. The metabisultesare similar in action to the bisultes and have been regarded as thehydrate of bisultes, and the reaction given abovewould be the same whena meta bisulte is employed.

It has been discovered that the composition of the present invention ismost effective in dissolving rust when the mixture contains about 60%sodium bisultite and about 40% sodium hydrosulfte. The composition ofthe invention is not limited to this specific ratio, however, as it hasalso been found that the ratio of sodium hydrosulte to sodium bisulfitemay be varied without destroying the effectiveness, `and especially therust and stain removing capabilities,`v` of the composition. It also isoften desirable to adjust the ratio in accordance with the stain beingtreated, v,the solution in which the treatment is carried out, and theconditions under which the treatment is conducted, Referring morespecifically to the case of dissolving and removing rust, FIG. 2 is achart illustrating the relationship between the composition em bodyingthe invention and the amount of rust dissolved. The chart of FIG. 2gives the relationship between the amount of rust dissolved and the rustremover composition. As shown on this chart, sodium hydrosulfite iscapable by itself of removing and dissolving rust to some extent. Forexample, the amount of rust dissolved per gram of rust removed when 100%sodium hydrosultte is employed, is indicated as 0.12 gram. `When,however, a rust remover composition containing 40% sodium hydrosulfiteand 60% sodium -bisulte is employed, 0.29 gram of rust was dissolved pergram of rust remover.

While it will be appreciated lby those skilled in the art that theadditions of even small amounts of sodium bisulfite to the sodiumhydrosulte would effect an improvement in the amount of rust dissolved,it has been found for most applications and it isjapplicants` preferredrange, lthat the rust remover composition contained between 25 and 75%sodium hydrosulfite and the remainder bisulte or equivalent such assodium meta-bisultite.

Patented-May 11, 1965l 'i :been recharged wit-hv salt rproduoed.

lI Jnder the usual conditions employed for water softener, it has been'foundf'that recharging of an iron fouled softener-,.or a softener in thepresence of water containing iron will not remove precipitated ironrust. In the operation. of anion .exchange resin or z eolite watersoftener withwater that contains quantities of iron, particularlydissolved ferrous iron, there isa gradual accumulation of, ironrust onthe ion exchange material. This is believed to be caused byairfoxid'ation of ferrous iron to ferrie iron, after which the rustprecipitates from the internal surfaces oftheaporous grains of the ionexchange mineral and thereby gradually clog the pores of the Igrains andcoat the surfaces so-that the ion exchangecapacity fory softening wateris' substantially reduced. In

"addition, it rhas been found vthat some of the rust becomes dislodgedduring normal use of the softener. This isgparticulnrlyobviousimmediately after the softenerhas brine so that rusty soft wateris =A solution to thisproblem `has been sought, and various cleaningagents or additives that could be incor- Qporated in the regeneratingsalt in order to solubilinev the. iron .rust.during .theI brineAregeneration have-been suggested. The requirements of such a materialare that. it

be ompatible with salt, be reactive and present in small fneutral in pH,*be non-toxibe easily washed from and .removed from the-softener bed,have little or no odo'r o'r Jtaste, be non-injurious lto the mineral,and be inexpensive and easy :to use. ,Among the suggested agents f orthis purpose is the compound sodium hydrosulfte. While materialhas beensuccessful to some extent, vitl 1as disadvantages vin that itis slow toact, requires a high vconcentratic'in to effect any vdegreeiof ironremoval, cre- --a'ts an odor, and vvsometimes lleaves a blackprecipitate r which is difficult 4to wash out of the softener or off ofthe surface being cleaned. l

' .The composition embodying the invention as described 4 above has beenfound'to have particular utility in removingiron rust from watersoftening and water .treatment equipment. The rust remover compositioncan be added by'itself or along with the salt employed to regenerate theion exchangeresin within the equipment. The use ofthe yru'stremover in abrine solution is extremely effective not onlyin removing'rust deposits'but also, when 4used continuously in small amounts, is effective tokeep the iron level extremely low. This effect is shown in PIG. 3.When-a water softener is regenerated with saltv only, vthe amount ofiron on the water softening agent orion exchangevresin builds up, `asshown in the upper -`curve of FIG. 3, infproportion to the number of relgeneration cycles".

This accumulation of iron rust'can be avoided, however, by employingapproximately 2% by weight of the above, described rust removercomposition, 'containing 40% sodium hydrosulte and 60% sodium bisulfte,'with the saltused'for regeneration. Using such` a composition,the'percentage of iron o n the ion exchange resin, remains -low asshownby the lower line of FIG. 3.

"while the use' of rust' remover campesinos in the ion -exchange resin'regeneration salt in an amount of about 2%, by weight has been'given asanrexample, it will be appreciatedthat the amount of rust remover can bevaried according to vfthe amount 'of iron in the water and the conditionofthe watersoftening equipment. If the iron content ofthe water is low,as little as 0.5% Iby weight Vrust. remover in the salt can be employed.On the other hand, if badly fouled equipment is to be ycleaned, the

' amount of rust remover inthe regeneration saltrnight desirably be asmuch as y QFor use in ion exchange resin equipment, the rust retmovercomposition can be mixed with dry salt (NaCl) land themixtureftableltd, Further, it is not necessary 4 l Y that the sodiumhydrosulfte and sodium bisulfite or melubisulfite .-be added as a mixedpowder or at the same time.

The ingredients can be added separately, although both.

must be present at the same time in order lto effect the desiredreaction.- The rustA remover composition embodying the present inventionis stable inl-water;,or a" brine solution for only a short time. vForthis reason,

it is preferably kept and stored a's a -d-ry powder and for ".wa'ter.lThe rust precipitation 4appears to grow on the concentrations, yreact"rapidly, be non-corrosive to iron and other metals :used the equipment,be essentially this reason tabletting the powder with a` water softenerlregenerating composition such as salt is desirable.

To use the Arust removing composition,v at. the time the salt is addedto the water softener a measured amount of the-:rust remover is added.If a# brine is to be used to regenerate the equipmentit is necessary toprepare only as much brine and ru'st removing agent as can be used inthe one regeneration. To clean a water softener bed which has becomefouled with iron, the equipment should be backwashed to remove `as muchfree ru'stas possible. `The softener is then recharged with salt brine't in the usual manner. Following thebrine, a rust remover .mixtureplu's a small amount of vsalt is passed through the softener to dissolvethe fixed rust.. The amount .of rust -remover composition employed willdepend upon the 'l condition of the equipment. It has generally Abeenfound 'that where the -use of the rust remover has notbeen `continuouslyemployed and where vthe eqll'ipmentis heavily coated with rust, aboutone lpound ofv rustvremover mixed with five pounds of salt, added eitheras asolid v or dissolved in two gallons `of water and added as a brine,

are recommended per cubic foot of resin. Additional treatments can beemployed until vthe softener mineral is free vfrom rust. ,Among thevariousways in which r'us't andstain removing compositions embodying theinvention can be used are n household detergents, cleansers, soaps and Ythe like..y The drypowder rust removeris preferably -incorporated in aysmall amount, say from about 1 to about 5% by weight, into'the'powdered cleansing'agent and the material kept in a closed containerprior to use. `It. has been found vthat by incorporating the stainremover ern,

bodying the invention -into detergents,"for example, which preferablethat the amount of 4stain remover in the cleanvsers be somewhat greaterthan -in detergents and soaps,

and 'it has been found that the use ofamounts somewhere in the 'range ofabout 5to about 10% bywe'ight produces-a satisfactory product from mostcleaning operations." Where the' rust deposits are heavy, somewhat moreof the stain removing agent must be used. It has been found, moreover,that the stain removing agent is more effective on heavydeposits whenused directly as a damp powder or in paste form. For example,application to a rusted surface is made by wetting the surface,

applying an amount "of the stain removing composition to a damp cloth,and rubbing the surface much in the mani.-

lner of using an abrasive cleanser. lThe stain removing composition canalso be employed in an admixture with a colloid forming substance suchas' carboxymethyl cel-y ylulose.l When this composition isV mixed with asmall .amount of water, a paste is formed which caribe applied 4 toheavily stained or rusted surfaces. The ,surface is then' If furtherapplications of` the rust thoroughly rinsed. remover are required, theforegoing steps are repeated. After the surface has been cleaned, it isprotected with a suitable paint or lacquer. f I lWhile the foregoinggives 'som illustrations-of possibilities for using the stain and 'rustrniver of present invention, other uses and applications will doubtofthe composition itself. It is accordingly the intention to cover suchmodifications, alternative uses and equivalents as determined by thespirit and scope of the appended claims.

To improve the reaction of the rust or stain removing agent with thecorroded metal surfaces, stained surfaces, etc., a surface active agentor synthetic detergent is desirably added. Such an agent should be a drypowder which is readily soluble when water is added to produce an`active surface wetting stain removing composition.

l Among the surface active agents finding particular utility are thealkyl aryl sulfonates and alkyl sulfates such as lauryl sulfate. Thesecompositions, generally the sulfated and sulfonated anionic surfaceactive agents, exist in the form of a dry powder which can be readilymixed i with the dry powder stain remover composition described above.

A dry powder composition of this character can be made with betweenabout 2 and about 5% by weight of a surface active agent such as sodiumalkyl aryl sulfonate. Other compositions can, of course, be producedusing different surface acting agents. Thus, various anionic agents suchas the carboxylic acids, sulfates, alkane sulfonic acids and alkylaromatic sulfonic acids can be employed. Cationic agents such as aminesand quarternary ammonium compounds might be employed, and nonionicagents such as polymeric propylene oxide-ethylene oxide agents. Also,alkyphenol-ethylene oxide condensates afford surface active anddetergent action.

If the stain removing composition is to be incorporated into a detergentsuch as the lauryl Vsulfate type of synthetic detergent, a small amountof the stain removing composif' tion is added to the synthetic detergentpowder.

For removing most stains from clothes, fabrics and the like, it has beenfound that about 0.5 to 2% by weight of the stain remover in a detergentgives satisfactorytresults. If the stains are heavy, however, additionalamounts of the stain remover may be required.

Referring to FIGURE 1, there is shown a process which can be employedfor manufacturing a rust removing composition embodying the foregoinginvention. The basic starting materials for such a process arecommercially produced sulfur and caustic soda (NaOH). The caustic sodais stored in a suitable tank from which it is pumped, through a suitablepump 11, along with the required amount of water from `a line 14, to thetop of a gas absorber column 15. Thesulfur is burned in a burner 16 andthe sulfur dioxide produced passes through l a blower 18 to the bottomof the gas absorber column 15. The sulfur dioxide is absorbed in thecaustic soda and water to produce a 10% sodium bisulte solution, whichleaves the gas absorber column through a bottom line 19. The scrubbedgases pass out of the top of the column through an outlet 20.

, The 10%.sodium bisulte solution'is then electrolyz'ed in anelectrolytic cell` 21. .-The electrolytic cell can be of anyconstruction known in the art. Shown diagrammatically in FIG. l is acell containing the usual graphite anodes 22 and the lead cathodes 23connected to a source .removed from the sodium bisuliite in solution,and the oxygen ions pass through the diaphragm and are discharged asoxygen gas from the anode. This results in the reduction of some of thesodium bisulfite to sodium hydrosulte and water. The reduction iscarried to the extent where approximately 40% of the sodium bisuliite isreduced to sodium hydrosulte, the remaining 60% of sodium bisultepassing unchanged through the electrolytic cell 2l.

The partially reduced bisulfite-hydrosulte solution is then directed toa suitable vacuum drier 25 and the composition is removed from the drieras a dry powder having the desired proportions of sodium bisulte andsodium hydrosulte. This composition can be used in the varabout 2% byweight ofa rust removing composition consisting essentially of ab''ut40% by weight sodium hydrosulte and about 60% by weightsodium bisulte.

3. A water softener regenerating composition in tabletted formconsisting essentially of sodium chloride regenerating salt and betweenabout 0.5% and about 20% by weight of a rust removing compositionconsisting essentially of about 40% by Weight sodium hydrosulte andabout 60%V by weight sodium bisulte.

4. A composition consisting essentially of surface active agent and anamount of from about 0.5 to about 20%v by weight -of the rust st ainremoving composition of claim 1.

5. A composition consisting essentially of surface active agent and aneffective amount of a rust stain removing composition consistingessentially of from about 40% by weight of an alkali hydrosulfite, acompound selected 4from the group consisting of the hydrosulfite ofsodium and potassium and about 60% of compound selected from the groupconsisting of the bisulte and metabisulfites of sodium and potassium. j

References Cited bythe Examiner UNITED STATES PATENTS JULIUS GREENWALD,Primary Examiner. ALBERT T. MYERS, Examiner.

1. A RUST STAIN REMOVING COMPOSITION CONSISTING ESSENTIALLY OF ABOUT 40%BY WEIGHT SODIUM HYDROSULFITE AND ABOUT 60% BY WEIGHT SODIUM BISULFITE.4. A COMPOSITION CONSISTING ESSENTIALLY OF SURFACE ACTIVE AGENT ANAMOUNT OF FROM ABOUT 0.5 TO ABOUT 20% BY WEIGHT OF THE RUST STAINREMOVING COMPOSITION OF CLAIM 1.